The invention relates to a control apparatus of the electromechanical type for opening and closing intake and/or exhaust valves for a thermal engine, particularly an internal combustion engine.
In an internal combustion engine the valves are opened or closed at precise moments of the working cycle. In most ordinary motors, the command for opening and closing is performed mechanically according to the position of the crankshaft. In recent years, electrochanical valve controls have been developed which offer the advantage of simplifying the design of the motor and permitting the timing and the durations of the opening and closing of the valves, which can be selected at will in order to optimize the performance of the motor.
Such electromechanical valve control apparatuss generally involve a magnetic pallet or plate cooperating with two electromagnets and two springs.
For this purpose the plate is generally in one piece with the end of a rod whose other end cooperates with the stem of the valve. The rod can also be integral with the stem of the valve. One of the electromagnets is designed to attract the plate to such a position that the valve is in the closed position. In this position one spring is compressed and the other relaxed, the compressed spring being then used to push the plate toward the other position, the one in which the valve is in the open position. The command from the closed position to the open position is performed by cutting off the power from the first electromagnet and by continued supply of power to the second electromagnet. In the open position, the first spring is relaxed and the second spring is compressed. This second spring pushes the plate, upon the opening position command, toward the closing position.
To limit power consumption by the valve operator, one and/or the other of the electromagnets is of the polarized type, i.e., a permanent magnet is provided in the magnetic circuit of the one and/or the other of the electromagnets. In this case, holding the valve in an open position and/or closed position does not require any current.